The present invention relates generally to a hinge for containers, and more particularly to a two-part hinge for use in semi-conductor wafer containers and boxes.
Containers are used in many applications within the semiconductor industry to protect components from contaminants, breakage and misplacement. These containers usually incorporate existing hinges, which typically comprise living hinges or traditional hinges with removable hinge pins or pintles which are received in barrels or knuckles of hinge segments.
These hinges are not without their drawbacks. With a living hinge, there is a tendency to resist flexation due to memory in the material. Thus, a container with a living hinge will not open and close freely within its operating range. Resistance must be overcome, and frequently the hinge must be overflexed in order to avoid reversion to a prior position. Over time, such hinges lose their effectiveness and eventually may fatigue and fail. Once such failure has occurred, the entire container must be scrapped. Additionally, if one section of the container breaks, the entire container must be scrapped.
With traditional hinge construction, hinge leaves are attached to each other by a pintle. The pintle is usually fabricated out of a different, more wear resistant material than the hinge leaves. Thus, after a period of time, the barrels or knuckles of the hinge leaves wear out. This results in improper operation of the hinge and container sealing ability suffers. Additionally, when the barrels or knuckles wear out, the pintle is prone to dislodgement and/or loss, thus rendering the hinge inoperative for its intended use. Another drawback is that pintles are often made out of metal, such as steel, which is prone to oxidation. As oxidants build up, the operation of the hinge suffers and becomes less efficient. And, depending upon the particular environment, the pintles can discolor or otherwise mar the hinge leaves. Moreover, metal is a very undesirable material for wafer carriers due to potential contamination problems.
Attempts have been made to solve the above-mentioned drawbacks. For example, U.S. Pat. No. 2,527,318 issued to Magnus, Oct. 24, 1950, discloses a plastic hinge construction for boxes and the like. In this patent, the hinge parts are integral with the container segments, with one of the hinge parts including a hinge pin, and the other hinge part including semicircular grooves and a resilient tongue member. When assembled, the tongue member exerts a force against the hinge pin to maintain the hinge pin in contact against the semicircular grooves.
U.S. Pat. No. 2,734,222 issued to Kiba, Feb. 14, 1956, discloses a hinge structure for molded boxes. This patent, like Magnus, teaches integral hinge construction. Assembly differs, however, in that the pintle ends of Kiba are received in a pair of bight portions and the pintle body is engaged by a stop to permanently retain the pintle ends within the bights. With Kiba, the stop is attached to a thinned wall portion of a container section, and the thinned wall portion is deflected by the pintle as it passes thereby. Note that the hinge is preferably assembled shortly after the container halves have been removed from their molds. This is because warm plastic is still relatively pliable and has not set. After assembly, and once the plastic has set, the assembled hinge is considered permanent.
The problem with the above-mentioned hinges is that they are structurally weak and/or they are not designed to be separated after assembly.
There is a need for a hinge which may be integrally formed with sections of a container, which may be easily assembled and disassembled, and which provides a strong, long lasting pivot joint.